In the course of the photographic process, the photographic material (films/paper) passes through a multistage process, e.g. development, washing, bleaching, washing, fixing, washing, stabilizing, drying or development, fixing, washing and drying.
So-called "wipers" were originally used to remove as much of the water adhering to the photographic material as possible before the drying process. This speeds up the drying process and saves energy which would otherwise be required for evaporating off the water adhering to the material.
These wipers are sometimes also used before and after the individual processing steps in order to reduce the amount of solutions carried over from one stage to the next. The devices used for this purpose may be, for example, rubber lips which strip the photographic material on one side or both.
Other devices are known in which the liquid adhering to the surface is blown off by compressed air. Yet another method is that of vacuum suction.
Whereas the production of a vacuum is technically relatively expensive, the simple use of compressed air has the disadvantage that the chemical solutions make contact in a finely atomized state with parts of the film where troublesome crystal residues are left after evaporation of the liquid.
Rubber lips, on the other hand, have the disadvantage that when used for prolonged periods with a material of a particular width, they undergo more wear at the edges than in the middle so that when there is a change in the format of the material the lips can no longer act uniformly over the whole width of the material. They must therefore be frequently replaced.
So-called squeezing rollers are also frequently used in photographic technology, the photographic material being passed between these rollers under pressure. The liquid adhering to the surface is thereby removed to some extent but liquids and chemicals present in the gelatine layers of the photographic material are not removed by this procedure. Such a pair of rollers is therefore not sufficiently effective.